Polyethylene with polycarbonate-siloxane for increased environmental stress crack resistance

ABSTRACT

A polyethylene composition having increased environmental stress crack resistance (ESCR) is comprised of a polymer blend of a high density polyethylene (HDPE) and a polycarbonate-siloxane copolymer. The polycarbonate-siloxane copolymer is present in the polymer blend in an amount of from 0.5 wt. % to 15 wt. % by total weight of the polymer blend. In a method of forming a polyethylene composition having increased ESCR, a HDPE is modified by combining the HDPE with a polycarbonate-siloxane copolymer in a polymer blend, the polycarbonate-siloxane copolymer being present in an amount of from 0.5 wt. % to 15 wt. % by total weight of the polymer blend. The polymer blend can be formed into an article of manufacture, such as a bottle cap.

CROSS REFERENCE TO RELATED APPLICATIONS

The application is a National Stage application of PCT/EP2019/062041,filed May 10, 2019, which claims the benefit of U.S. ProvisionalApplication No. 62/677,319, filed May 29, 2018.

TECHNICAL FIELD

The invention relates to high density polyethylene compositions thathave improved environmental stress crack resistance.

BACKGROUND

Synthetic polymeric materials, particularly thermoplastic resins, arewidely used in the manufacturing of a variety of end-use articlesranging from medical devices to food containers. Conventionalpolypropylene materials have long been used in processes likethermoforming, blow molding, coating, etc., requiring high melt strengthwhich could be achieved by increasing molecular weight and broadening ofmolecular weight distribution. Molecular weight and molecular weightdistribution can be modified in the polymerization process itself bychoosing particular process conditions and catalysts.

Polypropylene (PP) has widely been used to produce caps and closures. Toachieve a necessary cap strength, however, an inner liner (e.g., madefrom ethylene vinyl acetate (EVA), polyvinylchloride (PVC), butylrubber, or the like) is typically required to achieve the requisite sealproperties and organoleptic properties. Such two-layer caps are costly.On the other hand, high density polyethylene (HDPE) typically possessesrequisite stiffness, flow properties, and better organoleptic propertiesfor making one-piece closures, such as screw caps. HDPE, however, mostlylacks in its ability to resist cracking over time (as measured byenvironmental stress cracking resistance (ESCR) testing). Hence, thereis a need to improve ESCR performance of HDPE compositions.

Attempts have been made to improve such performance. These include theincorporation of C₄, C₆, and/or C₈ comonomers used duringpolymerization, which may be carried out in the vapor phase or insolution. Fine-tuning the molecular weight distribution (bi- ormulti-modal) has also been used as well as blending the polyethylenewith other polymers. Cross-linking of silane grafting of polyethylenehas also been used.

Given the growing trend of down-gauging of the plastic parts (forexample, caps and closure, bottles and containers) and the use ofplastic containers for storing aggressive chemicals (bleach bottles), anenhanced ESCR performance of plastics becomes more vital. For instance,a weight reduction of bottle caps from 3 g to 1.8-2.0 g, as currentlydemanded by many brand-owners, while still keeping its ESCR performance,is an emerging challenge.

While various methods exist to increase ESCR properties of polyethylene,many of these suffer in that they are cost prohibitive or applicableonly to the method of making the starting polyethylene materials insteadof to existing polyethylene materials. Thus, there is a continuing needfor polyethylene-based compositions having increased ESCR, particularlyfor those that are suitable for cap and closure applications.

SUMMARY

A polyethylene composition having increased environmental stress crackresistance comprises a polymer blend of a high density polyethylene(HDPE) and a polycarbonate-siloxane copolymer that is present in anamount of from 0.1 wt. % to 15 wt. % by total weight of the polymerblend, preferably of from 5.0 to 15.0 wt %.

In particular embodiments, the HDPE is at least one of an unimodal,bimodal HDPE and multimodal HDPE. The polycarbonate of thepolycarbonate-siloxane copolymer may be a bisphenol-A polycarbonate. Incertain instances, the polycarbonate-siloxane copolymer is a bisphenol-Aand eugenol end-capped siloxane copolymer.

The siloxane may be present in the polycarbonate-siloxane copolymer inan amount of from 2 mol % to 25 mol %.

The polymer blend may provide a molded article having an ESCR of atleast 40 hours as determined by ASTM D1693-15B. In certain instances,the polymer blend provides a molded article having an ESCR of from 40hours to 1000 hours as determined by ASTM D1693-15B.

The HDPE may be a copolymer with comonomers selected from 03 to OW alphaolefin monomers. The comonomers may be present in the HDPE copolymer inan amount of from 2 wt. % or less. In other instances the HDPE may be aneat HDPE.

The HDPE may have a melt flow ratio at 190° C. and 2.16 kg of 0.2 dg/minto 20 dg/min and/or a density of 945 kg/m³ to 965 kg/m³. In the contextof the present invention, density of the HDPE may be determined inaccordance with ISO 1183-1 (2012), method A, and the melt flow rate inaccordance with ISO 1133-1 (2011).

In some embodiments, the siloxane of the polycarbonate-siloxanecopolymer has a chain length of from 5 to 65 siloxane repeating units.The siloxane in the polycarbonate-siloxane may be a polymeric segmentforming part of a polymer chain, in combination with segments comprisingpolycarbonate repeating units.

The polymer blend may further comprise a polycarbonate homopolymer. Andin certain cases, the polymer blend may contain an additive of at leastone of a nucleating agent, a heat conductive agent, a tie agent, anantiblocking agent, an antistatic agent, an antioxidant, a neutralizingagent, an acid scavenger, a blowing agent, a crystallization aid, a dye,a flame retardant agent, a filler, an impact modifier, a mold releaseagent, an oil, another polymer, a pigment, a processing agent, areinforcing agent, a stabilizer, an UV resistance agent, a clarifyingagent, a slip agent, a flow modifying agent, and combinations thereof.

The polymer blend can be formed into an article of manufacture. Thearticle can include at least one of a film, a molded part, a container,a beverage container cap, a lid, a sheet, a pipe, a pipe coupling, abottle, a cup, a tray, a pallet, and a toy. The article may be formed byat least one of injection molding, blow molding, compression molding,sheet extrusion, film blowing, pipe extrusion, profile extrusion,calendaring, and thermoforming.

In particular embodiments, the polycarbonate-siloxane copolymer is abisphenol-A eugenol end-capped siloxane copolymer, with the siloxanebeing present in the polycarbonate-siloxane copolymer in an amount offrom 2 mol % to 25 mol %. In other embodiments, thepolycarbonate-siloxane copolymer may be present in an amount of from 0.2wt. % to 5 wt. % by total weight of the polymer blend.

In a method of forming a polyethylene composition having increasedenvironmental stress crack resistance, a high density polyethylene(HDPE) is modified by combining the HDPE with a polycarbonate-siloxanecopolymer in a polymer blend. The polycarbonate-siloxane copolymer maybe present in an amount of from 0.1 wt. % to 15 wt. % by total weight ofthe polymer blend. The polymer blend can be formed into one or morearticles of manufacture.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the embodiments described herein,and the advantages thereof, reference is now made to the followingdescriptions taken in conjunction with the accompanying figure, inwhich:

FIG. 1 is a scanning electron microscope (SEM) image of a polymer blendof bimodal HDPE incorporated with 10 wt. % polycarbonate-siloxanecopolymer; and

FIG. 2 is an unstained high resolution transmission electron microscope(TEM) image of a polymer blend of bimodal HDPE incorporated with 10 wt %polycarbonate-siloxane.

DETAILED DESCRIPTION

It has been discovered that the environmental stress crack resistance(ESCR) of high density polyethylene (HDPE) can be increased byincorporating an additive of a polycarbonate-siloxane copolymer. Thepolycarbonate-siloxane copolymer is incorporated into the HDPE bypolymer melt blending. The amount of polycarbonate-siloxane copolymerincorporated into the HDPE is selected so that the processability of theHDPE remains relatively unaffected while its ESCR performance isenhanced.

The HDPE polymers used in the polymer blend can include those preparedby any of the polymerization processes, which are in commercial use(e.g., a “high pressure” process, a slurry process, a solution processand/or a gas phase process) and with the use of any of the knowncatalysts (e.g., multisite catalysts such as Ziegler Natta catalysts,and/or single site catalysts such as chromium or Phillips catalysts,metallocene catalysts, and the like).

The HDPE polyethylene can be unimodal, bimodal, multimodal HDPE or acombination of these. As used herein, where the phrase or term “highdensity polyethylene” or “HDPE” are used without characterization asunimodal, bimodal or multimodal HDPE, the phrase or term should beconstrued as referring to any or all of them. Bimodal and/or multimodalHDPE can be made using an advance cascade process. HDPE can be obtainedfrom a commercial vendor. Non-limiting examples of suitable commerciallyavailable HDPE include those HDPE polymers marketed as SABIC® HDPE CC253and SABIC® HDPE CC254 (SABIC®, Kingdom of Saudi Arabia). In certainaspects, the polymer blends of the present invention do not includepolypropylene. In some embodiments, the polymer blends do not includelinear low density polyethylene (LLDPE).

The HDPE can be characterized by various properties such as a melt flowratio (MFR) at 190° C. and 2.16 kg, a density, ESCR, tensile strength atyield tensile modulus, tensile elongation at yield, Charpy notchedimpact strength (−30° C.), hardness or combinations thereof. The densityof the unimodal, bimodal or multimodal HDPE can be from 945 kg/m³ to 965kg/m³, or at least, equal to, and/or between any two of 945 kg/m³, 950kg/m³, 955 kg/m³, 960 kg/m³, and 965 kg/m³.

It should be noted in the description, if a numerical value,concentration or range is presented, each numerical value should be readonce as modified by the term “about” (unless already expressly somodified), and then read again as not so modified unless otherwiseindicated in context. Also, in the description, it should be understoodthat an amount range listed or described as being useful, suitable, orthe like, is intended that any and every value within the range,including the end points, is to be considered as having been stated. Forexample, “a range of from 1 to 10” is to be read as indicating each andevery possible number along the continuum between about 1 and about 10.Thus, even if specific points within the range, or even no point withinthe range, are explicitly identified or referred to, it is to beunderstood that the inventor appreciates and understands that any andall points within the range are to be considered to have been specified,and that inventor possesses the entire range and all points within therange.

In some embodiments, all or a portion of the HDPE component is unimodal.A MFR of unimodal HDPE at 190° C. and 2.16 kg can be from 0.2 dg/min to20 dg/min or at least, equal to, and/or between any two of 0.2 dg/min,0.3 dg/min, 0.4 dg/min, 0.5 dg/min, 0.75 dg/min, 1 dg/min, 1.25 dg/min,1.5 dg/min, 1.75 dg/min, 2 dg/min, 3 dg/min, 4 dg/min, and 5 dg/min, 6dg/min, 7 dg/min, 8 dg/min, 9 dg/min, 10 dg/min, 11 dg/min, 12 dg/min,13 dg/min, 14 dg/min, 15 dg/min, 16 dg/min, 17 dg/min, 18 dg/min, 19dg/min, and 20 dg/min. In particular embodiments, the MFR is from 0.5dg/min to 5 dg/min.

Tensile modulus and/or flexural modulus of unimodal HDPE can be from1000 MPa to 1300 MPa, or at least, equal to, and/or between any two of1000 MPa, 1050 MPa, 1100 MPa, 1150 MPa, 1200 MPa, 1250 MPa, and 1300MPa, as measured by ISO 527-2. Tensile and/or flexural strength at yieldof unimodal HDPE can be from 20 MPa to 40 MPa, or at least, equal to,and/or between any two of 20 MPa, 25 MPa, 30 MPa, 35 MPa, and 40 MPa, asmeasured by ISO 527-2.

In some embodiments, all or a portion of the HDPE component is bimodaland/or multimodal. Bimodal or multimodal HDPE can have a MFR at 190° C.and 2.16 kg of from 0.5 dg/min to 5 dg/min or at least, equal to, and/orbetween any two of 0.2 dg/min to 20 dg/min or at least, equal to, and/orbetween any two of 0.2 dg/min, 0.3 dg/min, 0.4 dg/min, 0.5 dg/min, 0.75dg/min, 1 dg/min, 1.25 dg/min, 1.5 dg/min, 1.75 dg/min, 2 dg/min, 3dg/min, 4 dg/min, and 5 dg/min, 6 dg/min, 7 dg/min, 8 dg/min, 9 dg/min,10 dg/min, 11 dg/min, 12 dg/min, 13 dg/min, 14 dg/min, 15 dg/min, 16dg/min, 17 dg/min, 18 dg/min, 19 dg/min, and 20 dg/min. In particularembodiments, the MFR is from 0.5 dg/min to 5 dg/min.

In the context of the present invention, density of the HDPE may bedetermined in accordance with ISO 1183-1 (2012), method A, and the meltflow rate in accordance with ISO 1133-1 (2011).

Tensile modulus of bimodal or multimodal HDPE can be from 1000 MPa to1300 MPa, or at least, equal to, and/or between any two of 1000 MPa,1050 MPa, 1100 MPa, 1150 MPa, 1200 MPa, 1250 MPa and 1300 MPa, asmeasured by ASTM D638. Tensile strength at yield of bimodal andmultimodal HDPE can be from 20 MPa to 40 MPa, or at least, equal to,and/or between any two of 20 MPa, 25 MPa, 30 MPa, 35 MPa, and 40 MPa, asmeasured by ASTM D638.

The Charpy notched impact strength of the HDPE component at −30° C. canbe from 3 kJ/m² to 6 kJ/m² or at least, equal to, and/or between any twoof 3 kJ/m², 4 kJ/m², 5 kJ/m², and 6 kJ/m².

In certain embodiments, the HDPE polyethylene component of the polymerblend will constitute homopolymers of ethylene. These may includehomopolymers solely of neat HDPE. In other embodiments, however, theHDPE polyethylene may include a polymer blend with non-HDPEpolyethylene. These may include low density polyethylene (LDPE), linearlow density polyethylene (LLDPE), and medium density polyethylene(MDPE). When such non-HDPE polyethylene is used it may be present in theHDPE polymer component in an amount of from 2 wt. %, 1.5 wt. %, 1 wt. %,0.5 wt. %, 0.1 wt. % or less. In other embodiments, the HDPEpolyethylene component can include copolymers of ethylene with at leastone C₃ to C₁₀ alpha olefin. Typically, this will be at least one of thealpha olefins of butene, hexene, and/or octene. In some embodiments thepolyethylene is a copolymer with 1-butene (polyethylene-1-butene) or1-hexene (polyethylene-1-hexene). When such copolymers are used, thenon-ethylene comonomer may be present in the HDPE copolymer in an amountof from 2 wt. %, 1.5 wt. %, 1 wt. %, 0.5 wt. %, 0.1 wt. % or less.

In certain embodiments, the HDPE polyethylene may be anun-functionalized neat HDPE with no functional groups along the polymerchain. In particular embodiments, the HDPE _(p)olyet_(hyl)ene does notinclude any anhydride modified HDPE.

The HDPE component, as described above, is used as a polymer blend incombination with a polycarbonate-siloxane copolymer. To impart thedesired ESCR characteristics of the final product, thepolycarbonate-siloxane copolymer is used in an amount of from 0.1 wt. %to 15 wt. % by total weight of the polymer blend. In particularembodiments, the polycarbonate-siloxane copolymer is used in an amountof from 0.1 wt. % to 15 wt. % by total weight of the polymer blend or atleast, equal to, and/or between any two of 0.1 wt. %, 0.2 wt. %, 0.3 wt.%, 0.4 wt. %, 0.5 wt. %, 0.6 wt. %, 0.7 wt. %, 0.8 wt. %, 0.9 wt. %, 1wt. %, 1.5 wt. %, 2 wt. %, 3 wt. %, 4 wt. %, 5 wt. %, 6 wt. %, 7 wt. %,8 wt. %, 9 wt. %, 10 wt. %, 11 wt. %, 12 wt. %, 13 wt. %, 14 wt. %, and15 wt. % by total weight of the polymer blend.

The polycarbonate siloxane copolymer component of the polymer blend mayhave an average molecular weight of from 10,000 to 60,000 or at least,equal to, and/or between any two molecular weights of 10,000, 15,000,20,000, 25,000, 30,000, 35,000, 40,000, 45,000, 50,000, 55,000, and60,000. The polycarbonate component of the polycarbonate-siloxanecopolymer may be present in an amount of from 75 mol % to 98 mol %, orat least, equal to, and/or between 75 mol %, 76 mol %, 77 mol %, 78 mol%, 79 mol %, 80 mol %, 81 mol %, 82 mol %, 83 mol %, 84 mol %, 85 mol %,86 mol %, 87 mol %, 88 mol %, 89 mol %, 90 mol %, 91 mol %, 92 mol %, 93mol %, 94 mol %, 95 mol %, 96 mol %, 97 mol %, and 98 mol %.

The carbonate monomers used to form the polycarbonate may includephosgene, dimethylcarbonate and/or diphenylcarbonate. In particularembodiments, one of the aromatic dihydroxy comonomer used for making thepolycarbonate-siloxane copolymer is a bisphenol-A. Comonomers that maybe used include those described in U.S. Pat. No. 7,365,124, which isincorporated herein by reference for such purpose. These include but arenot limited to 2,4′-dihydroxydiphenylmethane,bis(2-hydroxyphenyl)methane, bis(4-hydroxyphenyl)methane,bis(4-hydroxy-5-nitrophenyl)methane,bis(4-hydroxy-2,6-dimethyl-3-methoxyphenyl)methane,1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxy-2-chlorophenyl)ethane,2,2-bis(4-hydroxyphenyl)propane (bisphenol A);2,2-bis(3-chloro-4-hydroxyphenyl)propane;2,2-bis(3-bromo-4-hydroxyphenyl)propane;2,2-bis(4-hydroxy-3-methylphenyl)propane;2,2-bis(4-hydroxy-3-isopropylphenyl)propane;2;2-bis(3-t-butyl-4-hydroxyphenyl)propane;2,2-bis(3-phenyl-4-hydroxyphenyl)propane;2,2-bis(3,5-dichloro-4-hydroxyphenyl)propane;2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane;2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane;2,2-bis(3-chloro-4-hydroxy-5-methylphenyl)propane;2,2-bis(3-bromo-4-hydroxy-5-methylphenyl)propane;2,2-bis(3-chloro-4-hydroxy-5-isopropylphenyl)propane;2,2-bis(3-bromo-4-hydroxy-5-isopropylphenyl)propane;2,2-bis(3-t-butyl-5-chloro-4-hydroxyphenyl)propane;2,2-bis(3-bromo-5-t-butyl-4-hydroxyphenyl)propane;2,2-bis(3-chloro-5-phenyl-4-hydroxyphenyl)propane;2,2-bis(3-bromo-5-phenyl-4-hydroxyphenyl)propane;2,2-bis(3,5-disopropyl-4-hydroxyphenyl)propane;2,2-bis(3,5-di-t-butyl-4-hydroxyphenyl)propane;2,2-bis(3,5-diphenyl-4-hydroxyphenyl)propane;2,2-bis(4-hydroxy-2,3,5,6-tetrachlorophenyl)propane;2,2-bis(4-hydroxy-2,3,5,6-tetrabromophenyl)propane;2,2-bis(4-hydroxy-2,3,5,6-tetramethylphenyl)propane;2,2-bis(2,6-dichloro-3,5-dimethyl-4-hydroxyphenyl)propane;2,2-bis(2,6-dibromo-3,5-dimethyl-4-hydroxyphenyl)propane;2,2-bis(4-hydroxy-3-ethylphenyl)propane,2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane,2,2-bis(3,5,3′,5′-tetrachloro-4,4′-dihydroxyphenyl)propane,bis(4-hydroxyphenyl)cyclohexylmethane,2,2-bis(4-hydroxyphenyl)-1-phenylpropane,1,1-bis(4-hydroxyphenyl)cyclohexane;1,1-bis(3-chloro-4-hydroxyphenyl)cyclohexane;1,1-bis(3-bromo-4-hydroxyphenyl)cyclohexane;1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane;1,1-bis(4-hydroxy-3-isopropylphenyl)cyclohexane;1,1-bis(3-t-butyl-4-hydroxyphenyl)cyclohexane;1,1-bis(3-phenyl-4-hydroxyphenyl)cyclohexane;1,1-bis(3,5-dichloro-4-hydroxyphenyl)cyclohexane;1,1-bis(3,5-dibromo-4-hydroxyphenyl)cyclohexane;1,1-bis(4′-hydroxy-3′-methylphenyl) cyclohexane (DMBPC),1,1-bis(3,5-dimethyl-4-hydroxyphenyl)cyclohexane;4,4′-[1-methyl-4-(1-methyl-ethyl)-1,3-cyclohexanediol]bisphenol (1,3BHPM),4-[1-[3-(4-hydroxyphenyl)-4-methylcyclohexyl]-1-methyl-ethyl]-phenol(2,8 BHPM), 3,8-dihydroxy-5a, 10b diphenylcoumarano-2′,3′,2,3-coumarane(DCBP), 2-phenyl-3,3-bis(4-hydroxyphenyl)phthalimidine,1,1-bis(3-chloro-4-hydroxy-5-methylphenyl)cyclohexane;1,1-bis(3-bromo-4-hydroxy-5-methylphenyl)cyclohexane;1,1-bis(3-chloro-4-hydroxy-5-isopropylphenyl)cyclohexane;1,1-bis(3-bromo-4-hydroxy-5-isopropylphenyl)cyclohexane;1,1-bis(3-t-butyl-5-chloro-4-hydroxyphenyl)cyclohexane;1,1-bis(3-bromo-5-t-butyl-4-hydroxyphenyl)cyclohexane;1,1-bis(3-chloro-5-phenyl-4-hydroxyphenyl)cyclohexane;1,1-bis(3-bromo-5-phenyl-4-hydroxyphenyl)cyclohexane;1,1-bis(3,5-disopropyl-4-hydroxyphenyl)cyclohexane;1,1-bis(3,5-di-t-butyl-4-hydroxyphenyl)cyclohexane;1,1-bis(3,5-diphenyl-4-hydroxyphenyl)cyclohexane;1,1-bis(4-hydroxy-2,3,5,6-tetrachlorophenyl)cyclohexane; 1,1-bis(4-hydroxy-2,3,5,6-tetrabromophenyl)cyclohexane; 1,1-bis(4-hydroxy-2,3,5,6-tetramethylphenyl)cyclohexane; 1,1-bis(2,6-dichloro-3,5-dimethyl-4-hydroxyphenyl)cyclohexane;hydroxyphenyl)cyclohexane;1,1-bis(2,6-dibromo-3,5-dimethyl-4-1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(3-chloro-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane; 1,1-bis(3-bromo-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane; 1,1-bis(4-hydroxy-3-methylphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(4-hydroxy-3-isopropylphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(3-t-butyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(3-phenyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(3,5-dichloro-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(3,5-dibromo-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(3,5-dimethyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(3-chloro-4-hydroxy-5-methylphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(3-bromo-4-hydroxy-5-methylphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(3-chloro-4-hydroxy-5-isopropylphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(3-bromo-4-hydroxy-5-isopropylphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(3-t-butyl-5-chloro-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(3-bromo-5-t-butyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane;bis(3-chloro-5-phenyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(3-bromo-5-phenyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(3,5-disopropyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(3,5-di-t-butyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(3,5-diphenyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(4-hydroxy-2,3,5,6-tetrachlorophenyl)-3,3,5-trimethylcyclohexane;1,1-bis(4-hydroxy-2,3,5,6-tetrabromophenyl)-3,3,5-trimethylcyclohexane;1,1-bis(4-hydroxy-2,3,5,6-tetramethylphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(2,6-dichloro-3,5-dimethyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane;1,1-bis(2,6-dibromo-3,5-dimethyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane;4,4-bis(4-hydroxyphenyl)heptane, 4,4′-dihydroxy-1,1-biphenyl;4,4′-dihydroxy-3,3′-dimethyl-1,1-biphenyl;4,4′-dihydroxy-3,3′-dioctyl-1,1-biphenyl;4,4′-(3,3,5-trimethylcyclohexylidene)diphenol,4,4′-bis(3,5-dimethyl)diphenol, 4,4′-dihydroxydiphenylether;4,4′-dihydroxydiphenylthioether;1,3-bis(2-(4-hydroxyphenyl)-2-propyl)benzene;1,3-bis(2-(4-hydroxy-3-methylphenyl)-2-propyl)benzene;1,4-bis(2-(4-hydroxyphenyl)-2-propyl)benzene,1,4-bis(2-(4-hydroxy-3-methylphenyl)-2-propyl)benzenedihydroxydiphenylsulfone(BPS), 2,4′-dihydroxyphenyl sulfone, 4,4′-bis(4-hydroxyphenyl)methane,2,6-dihydroxynaphthalene; hydroquinone; resorcinol, C1-C3alkyl-substituted resorcinols,3-(4-hydroxyphenyl)-1,1,3-trimethylindan-5-ol,1-(4-hydroxyphenyl)-1,3,3-trimethylindan-5-ol, and2,2,2′,2′-tetrahydro-3,3,3′,3′-tetramethyl-1,1′-spirobi[1H-indene]-6,6′-diol.The most typical aromatic dihydroxy compound is Bisphenol A (BPA).

In some embodiments, an isosorbide comonomer can be used with the2-hydrocarbyl-3,3-bis(4-hydroxyaryl)phthalimidine monomer to producepolycarbonate copolymers.

The copolycarbonates may have an average molecular weight (Mw) of from3000 to approximately 150,000. In the context of the present invention,the average molecular weight of a polymer is to be understood to be theweight average molecular weight. In the context of the presentinvention, molecular weights are to be understood to be expressed ing/mol.

The siloxane is present in the polycarbonate-siloxane copolymer in anamount of from 2 mol % to 25 mol %, or at least, equal to, and/orbetween 2 mol %, 3 mol %, 4 mol %, 5 mol %, 6 mol %, 7 mol %, 8 mol %, 9mol %, 10 mol %, 11 mol %, 12 mol %, 13 mol %, 14 mol %, 15 mol %, 16mol %, 17 mol %, 18 mol %, 19 mol %, 20 mol %, 21 mol %, 22 mol %, 23mol %, 24 mol %, and 25 mol %. The siloxane of thepolycarbonate-siloxane copolymer may be a eugenol end-capped siloxane inparticular embodiments. In further embodiments, the siloxane of thepolycarbonate-siloxane copolymer may be composed of a chain of siloxaneunits composed of those siloxane D-units having the formula (R)₂SiO unitwhere R is a C1 to C4 alkane. The chain length of the siloxane repeatingD units may range from 5 to 65 units or at least, equal to, and/orbetween 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, and 65units.

In certain embodiments, the polymer blend of HDPE andpolycarbonate-siloxane copolymer may also contain a polycarbonatehomopolymer. The polycarbonate homopolymers may be present in an amountof from 0.1 wt. % to 40 wt. % by total weight of the polymer blend or atleast, equal to, and/or between any two of 0.1 wt. %, 0.2 wt. %, 0.3 wt.%, 0.4 wt. %, 0.5 wt. %, 0.6 wt. %, 0.7 wt. %, 0.8 wt. %, 0.9 wt. %, 1wt. %, 1.5 wt. %, 2 wt. %, 3 wt. %, 4 wt. %, 5 wt. %, 6 wt. %, 7 wt. %,8 wt. %, 9 wt. %, 10 wt. %, 11 wt. %, 12 wt. %, 13 wt. %, 14 wt. %, and15 wt. %, 16 wt. %, 17 wt. %, 18 wt. %, 19 wt. %, 20 wt. %, 21 wt. %, 22wt. %, 23 wt. %, 24 wt. %, 25 wt. %, 26 wt. %, 27 wt. %, 28 wt. %, 29wt. %, 30 wt. %, 31 wt. %, 32 wt. %, 33 wt. %, 34 wt. %, 35 wt. %, 36wt. %, 37 wt. %, 38 wt. %, 39 wt. %, and 40 wt. % by total weight of thepolymer blend.

The carbonate monomers used to form the polycarbonate homopolymer may bethe same as used for the polycarbonate component of thepolycarbonate-siloxane copolymer, as has been previously described.These may include phosgene, dimethylcarbonate and/or diphenylcarbonate.In particular embodiments, the polycarbonate of thepolycarbonate-siloxane copolymer is a bisphenol-A polycarbonate. Thepolyethylene compositions can further include at least one additive.Non-limiting examples of additives include a nucleating agent, a heatconductive agent, a tie agent, an antiblocking agent, an antistaticagent, an antioxidant, a neutralizing agent, an acid scavenger, ablowing agent, a crystallization aid, a dye, a flame retardant agent, afiller (hard or soft), an impact modifier, a mold release agent, an oil,another polymer, a pigment, a processing agent, a reinforcing agent, astabilizer (including light stabilizers), an UV resistance agent, aclarifying agent, a slip agent, a flow modifying agent, and combinationsthereof.

Non-limiting examples of nucleating agents include calcium carbonate(CaCO3), barium sulfate (BaSO4), silica (SiO2), kaolin, talc, mica,titania (TiO2), alumina (Al2O3), a zeolite, mono- or polycarboxylicaromatic acid, a dye, a pigment, metal carboxylates, metal aromaticcarboxylate, hexahydrophthalic acid metal salts, stearates, organicphosphates, bisamides, sorbitols, or a combination thereof. Anon-limiting example of metal aromatic carboxylate includes sodiumbenzoate.

In certain aspects, a heat conductive additive is present in the polymerblend in an amount of at least, equal to, and/or between any two of 0.01wt. %, 0.2 wt. %, 0.3 wt. %, 0.4 wt. %, 0.5 wt. %, 0.6 wt. %, 0.7 wt. %,0.8 wt. %, 0.9 wt. %, and 1.0 wt. % by total weight of the polymerblend. Non-limiting examples of heat conductive additive include,aluminum oxide, titanium dioxide, graphitic compounds, graphenes, boronnitride, aluminum nitride, zinc oxide

In certain aspects, a tie molecule is present in the polymer blend inamount of at least, equal to, and/or between any two of 0.01 wt. %, 0.2wt. %, 0.3 wt. %, 0.4 wt. %, 0.5 wt. %, 0.6 wt. %, 0.7 wt. %, 0.8 wt. %,0.9 wt. %, and 1.0 wt. % by total weight of the polymer blend.Non-limiting examples of tie molecule include, linear low densitypolyethylene, low density polyethylene, medium density polyethylene.

In certain aspects, a filler is present in the polymer blend in amountof at least, equal to, and/or between any two of 0.01 wt. %, 0.2 wt. %,0.3 wt. %, 0.4 wt. %, 0.5 wt. %, 0.6 wt. %, 0.7 wt. %, 0.8 wt. %, 0.9wt. %, 1.0 wt. %, 2.0 wt. %, 3.0 wt. %, 4.0 wt. %, 5.0 wt. %, 6.0 wt. %,7.0 wt. %, 8.0 wt. %, 9.0 wt. %, 10.0 wt. %, 20.0 wt. %, and 30.0 wt. %by total weight of the polymer blend. The filler can be a hard filler.Non-limiting examples of hard filler include, inorganic particulatefillers such as silica, calcium carbonate, inorganic layered fillerssuch as clays, mica. The filler can also be a soft filler. Non-limitingexamples of soft filler include, immiscible particulateelastomeric/polymeric resins. The filler can also be a hollow filler.Non-limiting examples of hollow fillers include, glass microspheres,plastic microspheres, ceramic microspheres such as cenospheres made upof alumino silicate microspheres, metallic microspheres made up ofaluminum and copper/silver microspheres, phenolic microspheres.

In certain aspects, a light stabilizer is present in the polymer blendin an amount of at least, equal to, and/or between any two of 0.01 wt.%, 0.2 wt. %, 0.3 wt. %, 0.4 wt. %, 0.5 wt. %, 0.6 wt. %, 0.7 wt. %, 0.8wt. %, 0.9 wt. %, and 1.0 wt. % by total weight of the polymer blend.The light stabilizer can be a hindered amine light stabilizer. The term“hindered amine light stabilizer” refers to a class of amine compoundshaving certain light stabilizing properties. Non-limiting examples, ofhindered amine light stabilizers (HALS) include1-cyclohexyloxy-2,2,6,6-tetramethyl-4-octadecylaminopiperidine;bis(2,2,6,6-tetramethylpiperidin-4-yl) sebacate;bis(1-acetoxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate;bis(1,2,2,6,6-pentamethylpiperidin-4-yl) sebacate;bis(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate;bis(1-octyloxy-2,2,6,6-tetramethylpiperidin-4-yl) sebacate;bis(1-acyl-2,2,6,6-tetramethylpiperidin-4-yl) sebacate;bis(1,2,2,6,6-pentamethyl-4-piperidyl)n-butyl-3,5-di-tert-butyl-4-hydroxybenzyl malonate;2,4-bis[(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)butylamino]-6-(2-hydroxyethylamino-s-triazine; bis(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)adipate;2,4-bis[(1-cyclohexyloxy-2,2,6,6-piperidin-4-yl)butylamino]-6-chloro-s-triazine;1-(2-hydroxy-2-methylpropoxy)-4-hydroxy-2,2,6,6-tetramethylpiperidine;1-(2-hydroxy-2-methylpropoxy)-4-oxo-2,2,6,6-tetramethylpiperidine;1-(2-hydroxy-2-methyl propoxy)-4-octadecanoyloxy-2,2,6,6-tetramethylpiperidine;bis(1-(2-hydroxy-2-methylpropoxy)-2,2,6,6-tetramethylpiperidin-4-yl)sebacate;bis(1-(2-hydroxy-2-methylpropoxy)-2,2,6,6-tetramethylpiperidin-4-yl)adipate; 2,4-bis{N-[1-(2-hydroxy-2-methylpropoxy)-2,2,6,6-tetramethylpiperidin-4-yl]-N-butylamino}-6-(2-hydroxyethylamino)-s-triazine;4-benzoyl-2,2,6,6-tetramethylpiperidine;di-(1,2,2,6,6-pentamethylpiperidin-4-yl) p-methoxybenzylidenemalonate;2,2,6,6-tetramethylpiperidin-4-yl octadecanoate;bis(1-octyloxy-2,2,6,6-tetramethylpiperidyl) succinate;1,2,2,6,6-pentamethyl-4-aminopiperidine;2-undecyl-7,7,9,9-tetramethyl-1-oxa-3,8-diaza-4-oxo-spiro[4,5]decane;tris(2,2,6,6-tetramethyl-4-piperidyl) nitrilotriacetate;tris(2-hydroxy-3-(amino-(2,2,6,6-tetramethylpiperidin-4-yl)propyl)nitrilotriacetate;tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butane-tetracarboxylate;tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-butane-tetracarboxylate;1,1′-(1,2-ethanediyl)-bis(3,3,5,5-tetramethylpiperazinone);3-n-octyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decan-2,4-dione;8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro[4.5]decane-2,4-dione;3-dodecyl-1-(2,2,6,6-tetramethyl-4-piperidyl)pyrrolidin-2,5-dione;3-dodecyl-1-(1,2,2,6,6-pentamethyl-4-piperidyl)pyrrolidine-2,5-dione;N,N′-bis-formyl-N,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine;reaction product of2,4-bis[(1-cyclohexyloxy-2,2,6,6-piperidin-4-yl)butylamino]-6-chloro-s-triazinewith N,N′-bis(3-aminopropyl)ethylenediamine); condensate of1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinicacid; condensate ofN,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)-hexamethylenediamine and4-tert-octylamino-2,6-dichloro-1,3,5-triazine; condensate ofN,N′-bis(2,2,6,6-tetramethyl-4-piperidyl)-hexamethylenediamine and4-cyclohexylamino-2,6-dichloro-1,3,5-triazine; condensate ofN,N′-bis-(2,2,6,6-tetramethyl-4-piperidyl)hexamethylenediamine and4-morpholino-2,6-dichloro-1,3,5-triazine; condensate ofN,N′-bis-(1,2,2,6,6-pentamethyl-4-piperidyl)hexamethylenediamine and4-morpholino-2,6-dichloro-1,3,5-triazine; condensate of2-chloro-4,6-bis(4-n-butylamino-2,2,6,6-tetramethylpiperidyl)-1,3,5-triazine and 1,2-bis(3-aminopropylamino)ethane;condensate of2-chloro-4,6-di-(4-n-butylamino-1,2,2,6,6-pentamethylpiperidyl)-1,3,5-triazineand 1,2-bis-(3-aminopropylamino)ethane; a reaction product of7,7,9,9-tetramethyl-2-cycloundecyl-1-oxa-3,8-diaza-4-oxospiro[4,5]decaneand epichlorohydrin; poly[methyl,(3-oxy-(2,2,6,6-tetramethylpiperidin-4-yl)propyl)]siloxane, CAS#182635-99-0; reaction product of maleic acidanhydride-C18-C22-α-olefin-copolymer with2,2,6,6-tetramethyl-4-aminopiperidine; oligomeric condensate of4,4′-hexamethylenebis(amino-2,2,6,6-tetramethylpiperidine) and2,4-dichloro-6-[(2,2,6,6-tetramethylpiperidin-4-yl)butylamino]-s-triazineend-capped with 2-chloro-4,6-bis(dibutylamino)-s-triazine; oligomericcondensate of4,4′-hexamethylenebis(amino-1,2,2,6,6-pentaamethylpiperidine) and2,4-dichloro-6-[(1,2,2,6,6-pentaamethylpiperidin-4-yl)butylamino]-s-triazineend-capped with 2-chloro-4,6-bis(dibutylamino)-s-triazine; oligomericcondensate of 4,4′-hexamethylenebis(amino-1-propoxy-2,2,6,6-tetramethylpiperidine) and2,4-dichloro-6-[(1-propoxy-2,2,6,6-tetramethylpiperidin-4-yl)butylamino]-s-triazineend-capped with 2-chloro-4,6-bis(dibutylamino)-s-triazine; oligomericcondensate of 4,4′-hexamethylenebis(amino-1-acyloxy-2,2,6,6-tetramethylpiperidine) and2,4-dichloro-6-[(1-acyloxy-2,2,6,6-tetramethylpiperidin-4-yl)butylamino]-s-triazineend-capped with 2-chloro-4,6-bis(dibutylamino)-s-triazine; and productobtained by reacting (a) with (b) where (a) is product obtained byreacting 1,2-bis(3-aminopropylamino)ethane with cyanuric chloride and(b) is (2,2,6,6-tetramethyl piperidin-4-yl)butylamine. Also included arethe sterically hindered N—H, N-methyl, N-methoxy, N-hydroxy, N-propoxy,N-octyloxy, N-cyclohexyloxy, N-acyloxy and N-(2-hydroxy-2-methylpropoxy)analogues of any of the above mentioned compounds. Non-limiting examplesof commercial light stabilizer are available from BASF under the tradename Uvinul® 4050H, 4077H, 4092H, 5062H, 5050H, 4092H, 4077H, 3026,3027, 3028, 3029, 3033P, and 3034 or Tinuvin® 622.

Anti-static agents can be used to inhibit accumulation of dust onplastic articles. Antistatic agents can improve the electricalconductivity of the plastic compositions, and thus dissipate any surfacecharges, which develop during production and use. Thus, dust particlesare less attracted to the surface of the plastic article, and dustaccumulation is consequently reduced. In certain aspects of the presentinvention, the antistatic agent can be a glycerol monostearate. Thepolymer blend can include an anti-static agent in an amount of at least,equal to, and/or between any two 0.01 wt. %, 0.2 wt. %, 0.3 wt. %, 0.4wt. %, 0.5 wt. %, 0.6 wt. %, 0.7 wt. %, 0.8 wt. %, 0.9 wt. %, and 1 wt.% by total weight of the polymer blend.

A lubricant can be added to a polymer blend to improve the mold-makingcharacteristics. The lubricant can be a low molecular compound from agroup of fatty acids, fatty acid esters, wax ester, fatty alcohol ester,amide waxes, metal carboxylate, montanic acids, montanic acid ester, orsuch high molecular compounds, as paraffins or polyethylene waxes. Incertain aspects of the present invention, the lubricant is a metalstearate. Non-limiting examples of metal stearates include zincstearate, calcium stearate, lithium stearate or a combination thereof,preferably calcium stearate. The polymer blend can include a lubricantin an amount of at least, equal to, and/or between any two of 0.01 wt.%, 0.2 wt. %, 0.3 wt. %, 0.4 wt. %, 0.5 wt. %, 0.6 wt. %, 0.7 wt. %, 0.8wt. %, 0.9 wt. %, and 1 wt. % by total weight of the polymer blend.

An antioxidant can provide protection against polymer degradation duringprocessing. Phosphites are known thermal oxidative stabilizing agentsfor polymers and other organic materials. The antioxidant can be aphosphite-based antioxidant. In certain aspects phosphite-antioxidantsinclude, but are not limited to, triphenyl phosphite, diphenylalkylphosphites, phenyldialkyl phosphites, tris(nonylphenyl)phosphite,trilauryl phosphite, trioctadecyl phosphite, distearyl pentaerythritoldiphosphite, tris(2,4-di-tert-butylphenyl)phosphite, diisodecylpentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl)pentaerythritoldiphosphite tristearyl sorbitol triphosphite, andtetrakis(2,4-di-tertbutylphenyl)-4,4′-biphenylene diphosphonite,bis(2,4-dicumylphenyl)pentaerythritol diphosphite. The polymer blend caninclude an antioxidant in an amount of at least, equal to, and/orbetween any two of 0.01 wt. %, 02 wt. %, 0.3 wt. %, 0.4 wt. %, 0.5 wt.%, 0.6 wt. %, 0.7 wt. %, 0.8 wt. %, 0.9 wt. %, and 0.1 wt. % by totalweight of the polymer blend. Non-limiting examples of commerciallyavailable antioxidants include Irganox 1010 available from BASF, orDoverphos S9228T available from Dover Chemical Company.

In forming the composition, the various components of the HDPE andpolycarbonate-siloxane copolymer, which may be in the form of pellets,powder, or fluff, along with any additives, can be dry blended. Thesematerials combined in a customary mixing machine, in which the HDPE andpolycarbonate-siloxane copolymer are mixed with the optional additives.The optional additives can be added at the end or during the processingsteps to produce the polymer blend. Suitable machines for such mixingare known to those skilled in the art. Non-limiting examples includemixers, kneaders, extruders, and molders. These materials are then feddirectly into the feed zone of an extruder. In certain aspects, theprocess can be carried out in an extruder and introduction of theadditives may occur during processing. Non-limiting examples of suitableextruders include single-screw extruders, counter-rotating andco-rotating twin-screw extruders, planetary-gear extruders, ringextruders, or co-kneaders. The process can be performed at a temperaturefrom 160° C. to 280° C.

In some embodiments, the HDPE and polycarbonate-siloxane copolymer, andoptionally one or more additives, used to produce the polymer blend ofthe present invention can be melt-extruded by following typicalprocedures of weighing the required amounts of the HDPE,polycarbonate-siloxane copolymer and other additives, followed by dryblending, and then feeding the mixture into a main feeder of atwin-screw co-rotating extruder (length/diameter (L/D) ratio of 25:1 or40:1) to obtain the final composition. The HDPE, polycarbonate-siloxanecopolymer, or blend thereof can be subjected to an elevated temperaturefor a sufficient period of time during blending. The blendingtemperature can be above the softening point of the polymers. In certainaspects, the extrusion process can be performed at a temperature from160° C. to 280° C. The copolymer can be added along with other additivesin-line and prior to pelletization of HDPE resin during the productionprocess. The amounts of polycarbonate-siloxane copolymer combined withthe HDPE can be adjusted to provide those weight amounts previouslydiscussed.

Additives can be premixed or added individually to the polymer blend orthe different components thereof. By way of example, the additives ofthe present invention can be premixed such that the blend is formedprior to adding it to the HDPE or the polycarbonate-siloxane copolymer.The additive-containing blend thereof can be subjected to an elevatedtemperature for a sufficient period of time during blending and/orincorporation of additives. Incorporation of additives into thepolyolefin resin can be carried out, for example, by mixing theabove-described components using methods customary in processtechnology. The blending temperature can be above the softening point ofthe polymers. In certain aspects, a process can be performed at atemperature from 160° C. to 280° C. Such “melt mixing” or “meltcompounding” results in uniform dispersion of the present additives inthe HDPE and/or polycarbonate-siloxane copolymer.

Articles of manufacture (e.g., caps) that include the polymer blend canhave a higher ESCR than articles of manufacture made from HDPE withoutthe polycarbonate-siloxane copolymer (i.e., the HDPE used to prepare theblend). In some embodiments, the articles of manufacture of the presentinvention have an ESCR that is 200% to 1000% greater than the ESCRvalues of HDPE articles of manufacture with the same configuration usingthe same HDPE without the use of the polycarbonate-siloxane copolymer.The ESCR values can be at least, equal to, or between any two of 200%,300%, 400%, 500%, 600%, 700%, 800%, 900% and 1000% greater than the ESCRHDPE values without the use of polycarbonate-siloxane copolymer. Asexemplified in the Examples section and throughout the specification,polymer blend containing articles of manufacture of the presentinvention can have an ESCR values from at least 20 hours to 1000 hours(e.g., 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150,160, 170, 180, 190, 200, 300, 400, 500, 600, 700, 800, 900, and 1000,and any range or value there between and including the endpoints). Incontrast HDPE articles of manufacture without the polycarbonate-siloxanecopolymer, can have an ESCR values of less than but not equal to 20hours.

The polymer blend compositions formed as described are normallycollected as pellets, which can be stored for a time or employedimmediately in a forming process. The forming processes can includeinjection molding, blow molding, compression molding, sheet extrusion,film blowing, pipe extrusion, profile extrusion, calendaring,thermoforming, rotomolding, or combinations thereof. The final formedarticles can be, for instance, molded parts, sheets, films, or fibers.Examples of molded parts include a cap, a bottle cap, a container, alid, a sheet, a pipe, a pipe coupling, a bottle, a cup, a tray, apallet, or a toy, or combinations thereof. Caps can be injection and/orcompression molded. The caps may be threaded or non-threaded caps forselectively closing off openings to bottles or other containers. Suchcaps can be used in a variety of food and non-food applications. By wayof example, caps that include the polymer blend of the present inventioncan be used with containers for storing still water, carbonatedbeverages, pressurized beverages, or the like.

The invention, in a certain embodiment, also relates to the use in apolymer blend comprising high-density polyethylene of apolycarbonate-siloxane copolymer present in an amount of from 0.1 wt. %to 15 wt. %, preferably of from 5.0 to 15.0 wt %, by total weight of thepolymer blend, for increase of the environmental stress crack resistanceof a polymer composition comprising the blend.

The following examples serve to further illustrate various embodimentsand applications.

EXAMPLES Example 1

A polycarbonate-siloxane copolymer containing 20 mol % siloxane with 45siloxane repeating units (—O—Si(CH₃)₂—) and a molecular weight (MW) ofapproximately 30,000 (calculated w.r. to polystyrene monodispersedstandard) was dry mixed in different amounts of from 5 wt. % to 10 wt. %with commercially available HDPE. The HDPE used was SABIC® HDPE CC253and SABIC® HDPE CC254. SABIC® HDPE CC253 is a unimodal HDPE having a MFRat 190° C. and 2.16 kg of 1.8 dg/min and a density of 952 kg/m³. SABIC®HDPE CC254 is a bimodal HDPE having a MFR at 190° C. and 2.16 kg of 2.1dg/min and a density of 953 kg/m³. For comparison purposes, neat HDPEwithout any polycarbonate-siloxane copolymer was also tested. Thedifferent mixtures were fed into a hopper of a ZSK-25 mm 6 barreltwin-screw extruder with an L/D ratio of 25:1. The operating parametersused are set forth in Table 1 below:

TABLE 1 Barrel-1 (Attached with Hopper) Temp. = 160° C. Barrel-2 Temp. =185° C. Barrel-3 Temp. = 195° C. Barrel-4 Temp. = 195° C. Barrel-5 Temp.= 200° C. Barrel-6 (Die) Temp. = 210° C. Screw Speed 250 rpm Feed Rate6.8 kg/hr Batch Size 600 g

The torque measured during the melt extrusion of the neat and formulatedHDPE was in the range of 28-34%, indicating that the processibility ofHDPE was not hampered significantly with low/high molecular weightpolycarbonate-siloxane copolymer.

Example 2

The pellets obtained after the melt extrusion of Example 1 werecompression molded into 1.85 mm to 1.95 mm thick sheets at a temperatureof 195° C.-210° C., with a holding time of 5 min and a cooling time of 5min. No visual inhomogeneity was evident in the compression sheets. Thecompression molded sheets, both the neat and formulated HDPE, were thenevaluated for ESCR performance according to ASTM D1693-15B (Bell Test).

The compression molded sheets were cut into test specimens having alength of 38 mm and width of 13 mm. A notch of 0.5 mm depth was createdat the center of each test specimen prior to storing it in a conditionedenvironment of 23° C. and humidity of 55% RH. The conditioned specimenswere U-bent with the aid of a jig. Ten of the bent specimens for eachneat and formulated HDPE materials were placed in an aluminum sampleholder and subsequently placed inside a test tube filled with 10% v/vaqueous solution of Igepol CO-630 (nonylphenoxy poly(ethyleneoxy)ethanol, CAS 68412-54-4). The mouth of the test tube was closed with arubber cork wrapped with aluminum foil. The test specimens placed in thetest tube filled with 10% v/v Igepol CO-630 aqueous solution wasimmersed in an oil bath maintained at 50° C. The time it took to observethe formation of cracks in the test specimens were regularly noted. Thetime taken for 50% of the specimens (i.e., 5 out of the 10 specimens) tofail (i.e., crack) were reported to infer the ESCR performance of thegiven composition.

The ESCR performance of the neat HDPE and formulated HDPE incorporatingthe polycarbonate-siloxane copolymer are presented in Table 2 below:

TABLE 2 Time to 50% Fail Composition (hr) CC253 (Unimodal HDPE) 12 CC254(Bimodal HDPE) 16 CC253 = 5 wt. % PC-siloxane 21 CC253 = 10 wt. %PC-siloxane 32 CC254 = 5 wt. % PC-siloxane 36 CC254 = 10 wt. %PC-siloxane 70

As can be seen from Table 2, the observed time for 50% of the samples tofail for unimodal (CC253) and bimodal (CC254) HDPE was 12 and 16 hrs,respectively. The time for 50% of the samples to fail is found to be 2-3times higher for the HDPE compositions incorporating the 5 wt. % and 10wt. % polycarbonate-siloxane copolymer. Noticeably, not even a singlecrack was observed in the bimodal HDPE incorporating 10 wt. %polycarbonate-siloxane copolymer in any of the ten samples even after 35hrs.

Melt mass flow rate (MFR) of neat unimodal (CC253) and bimodal (CC254)HDPE resins measured at 190° C. with a load of 2.16 Kg by ISO1133-1:2011 method, along with that of a blend of bimodal HDPE (90 wt %)and polycarbonate-siloxane copolymer (10 wt %) are depicted in the Table3 below. The standard deviation observed during the MFR measurements is0.1 g/10 min.

TABLE 3 MFR (g/10 Composition min) CC253 (Unimodal HDPE) 1.80 CC254(Bimodal HDPE) 1.97 CC254 + 10 wt. % PC-siloxane 2.11

As can be seen from Table 3, the observed MFR values for unimodal(CC253) and bimodal (CC254) HDPE was 1.8 and 1.97 g/10 min,respectively. In comparison, the MFR value for the bimodal HDPEcomposition incorporating 10 wt. % polycarbonate-siloxane copolymer is2.11 g/10 min. This result indicates that the melt viscosity/flowcharacteristics of HDPE resins remain mostly unaffected with theincorporation of 10 wt % polycarbonate-siloxane copolymer, though such10 wt % polycarbonate-siloxane copolymer incorporated HDPE compositionsexhibited a superior ESCR performance.

The unstained scanning electron microscope (SEM) image of a blend ofbimodal HDPE (CC254) incorporated with 10 wt. % polycarbonate-siloxanecopolymer is depicted in the FIG. 1 . As seen from the FIG. 1 , thepolycarbonate-siloxane copolymer is dispersed within HDPE matrix withaggregate size ranging from 0.5-10 μm. Moreover, there is fairly a goodinterfacial adhesion of aggregates of polycarbonate-siloxane copolymerwith HDPE matrix.

The unstained high resolution transmission electron microscope (TEM)image of a blend of bimodal HDPE (CC254) incorporated with 10 wt %polycarbonate-siloxane copolymer is depicted in the FIG. 2 . As seenfrom FIG. 2 , the dark domains of siloxane are randomly distributed inthe PC-siloxane aggregates dispersed within the HDPE matrix.

The invention claimed is:
 1. A polyethylene composition having increasedenvironmental stress crack resistance, the composition comprising apolymer blend of a high density polyethylene (HDPE) and apolycarbonate-siloxane copolymer present in an amount of from 7 wt. % to15 wt. % by a total weight of the polymer blend, wherein the highdensity polyethylene is present in an amount of 85 wt. % to 93 wt. % bythe total weight of the polymer blend.
 2. The composition of claim 1,wherein the HDPE is at least one of an unimodal and a bimodal HDPE. 3.The composition of claim 1, wherein the polycarbonate of thepolycarbonate-siloxane copolymer is a bisphenol-A polycarbonate.
 4. Thecomposition of claim 1, wherein the polycarbonate-siloxane copolymer isa bisphenol-A and eugenol end-capped siloxane copolymer.
 5. Thecomposition of claim 1, wherein the siloxane is present in thepolycarbonate-siloxane copolymer in an amount of from 2 mol % to 25 mol%.
 6. The composition of claim 1, wherein the polymer blend provides amolded article having an ESCR of at least 40 hours as determined by ASTMD1693-15B.
 7. The composition of claim 1, wherein the HDPE is acopolymer with comonomers selected from C₃ to C₁₀ alpha olefin monomers,the comonomers being present in the HDPE copolymer in an amount of from2 wt. % or less.
 8. The composition of claim 1, wherein the HDPE has amelt flow rate at 190° C. and 2.16 kg of 0.2 dg/min to 20 dg/min and/ora density of 945 kg/m³ to 965 kg/m³.
 9. The composition of claim 1,wherein the siloxane of the polycarbonate-siloxane copolymer has a chainlength of from 5 to 65 siloxane repeating units.
 10. The composition ofclaim 1, wherein the polymer blend further comprises a polycarbonatehomopolymer.
 11. The composition of claim 1, further comprising anadditive of at least one of a nucleating agent, a heat conductive agent,a tie agent, an antiblocking agent, an antistatic agent, an antioxidant,a neutralizing agent, an acid scavenger, a blowing agent, acrystallization aid, a dye, a flame retardant agent, a filler, an impactmodifier, a mold release agent, an oil, another polymer, a pigment, aprocessing agent, a reinforcing agent, a stabilizer, an UV resistanceagent, a clarifying agent, a slip agent, a flow modifying agent, andcombinations thereof.
 12. An article comprising the composition ofclaim
 1. 13. A method of manufacture of an article, comprising injectionmolding, blow molding, compression molding, sheet extrusion, filmblowing, pipe extrusion, profile extrusion, calendaring, orthermoforming the composition of claim
 1. 14. A method of forming apolyethylene composition having increased environmental stress crackresistance, the method comprising modifying a high density polyethylene(HDPE) by combining the HDPE with a polycarbonate-siloxane copolymer ina polymer blend, the polycarbonate-siloxane copolymer being present inan amount of from 7 wt. % to 15 wt. % by total weight of the polymerblend, wherein the high density polyethylene is present in an amount of85 wt. % to 93 wt. % by the total weight of the polymer blend.
 15. Thecomposition of claim 6, wherein the polymer blend provides a moldedarticle having an ESCR of from 40 hours to 1000 hours as determined byASTM D1693-15B.
 16. The polyethylene composition of claim 1, wherein theHDPE is a bimodal HDPE.
 17. A polyethylene composition having increasedenvironmental stress crack resistance, the composition comprising apolymer blend of: a high density polyethylene, a polycarbonate-siloxanecopolymer, and a polycarbonate homopolymer, wherein the high densitypolyethylene is present in an amount of 45 wt. % to 92.1 wt. %, thepolycarbonate-siloxane copolymer is present in an amount of 7 wt. % to15 wt. %, and the polycarbonate homopolymer is present in an amount of0.1 wt. % to 40 wt. %, each based on a total weight of the polymerblend.
 18. The article of claim 12, wherein the article is a container,a beverage container cap, a lid, a sheet, a pipe, a pipe coupling, abottle, a cup, a tray, a pallet, or a toy.
 19. An article comprising apolyethylene composition having increased environmental stress crackresistance, the composition comprising a polymer blend of a high densitypolyethylene (HDPE) and a polycarbonate-siloxane copolymer present in anamount of from 7 wt. % to 15 wt. % by a total weight of the polymerblend, wherein the article is a cap or lid.